Due to its proven low implementation cost, reliability, and relative simplicity of installation and maintenance, Ethernet's popularity has grown to the point that nearly all data traffic on the Internet originates or terminates with an Ethernet connection. With increasing demands of data rates, 10 Gigabit Ethernet, normally referred to as 10 GbE, nowadays becomes the natural evolution and the widely adopted technology both in telecommunication and data communication networks.
A study group established with IEEE802.3 specifies the standards used for 10 GbE. One of the most interesting 10GbE standards refer to 10GBASE-CX4 (IEEE802.3ak) that specifies a physical layer device (PHY) for providing 10 Gb/ s over 4-lane copper cables, i.e. the so-called CX4 cable, which is similar to the corresponding varieties used in the known InfiniBand™ and DensiShield™ technologies. The introduction of 10GBASE-CX4 gains its popularity for use in data communication networks mainly due to advantages of low per-port cost, low power consumption and low latency.
FIG. 1 is a simplified schematic overview exemplifying a conventional network configuration comprising an IP based host system 100 which is interconnected with an IP transport network 102 via two separate lines, namely a working line, comprising a first pair of link paths 105a/105b, and a protecting line, comprising a second pair of link paths 105a′/105b′, where the protecting line has a main purpose of providing for redundancy in the network configuration.
For providing both lines and equipment protection, two switches 101a,101a', typically 10GbE switches, belonging to the host system is connected to its remote link partner, i.e. IP transport network 102, for the link path redundancy, via a respective router 103a,130a', typically a 10GbE router. Here, one pairing of a switch and router is used for the working line 105a/105b and the other pair is used for the protection line 105a'/105b', respectively. If a link failure occurs in the working line, the redundancy protection systems used by any of the IP based host system 100 and the IP transport network 102 will switch traffic from the failing working line to the protection line, or vice versa if the failing working line is recovered.
The 10GBASE-CX4 protocol which is a typical protocol for supporting an interconnection e.g. via a CX4 cable, specifies a maximum working distance which is limited to 15 m only. Such a limited working distance makes it difficultly to cover the basic demand in the telecom network, which typically ranges from a 200 m working distance for interconnecting applications up to a working distance of a few tens of km for long-haul applications. In order to reach a desired working distance, a media converter system, or more specifically a 10GbE media converter system, is needed for the 10GBASE-CX4 based host system to connect the remote link partner.
In order to meet the requirements of longer operating distances a new solution for the system described above with reference to FIG. 1 will be needed. FIG. 2 is another simplified schematic overview, exemplifying an alternative network configuration where two media converter systems, such as e.g. 10GbE media converter systems, have been deployed into the link paths between the switches 101a,101a' and the routers 103a,103a' for the main purpose of increasing the operating link distance. With the help of media converter systems, a link distance up to 40,000 m can be achieved.
The media converter system typically converts a copper-based formatted signal, i.e. 10GBASE-CX4, into fiber-optic based formatted signals, such as e.g. 10GBASE-SR/ -IR/ -ER specified by IEEE802.3ae, or 10GBASE-IRM specified by IEEE802.3aq. Since the media converter system only works at the physical network layer, it makes the whole conversion process transparent to the higher layer network devices, e.g. the Ethernet switches, which imply that it will not introduce any interference with higher layer functions in the network.
A media converter may e.g. be used for supporting a special application where the system of the remote link partner, e.g. a 1GbE switch, is designed to run a low data rate with the fiber-optic based 1000Base-X protocol. With the help of a SFP1000Base-ZX transceiver module and Single mode optical fibers (SMF), it may even be possible for a 10GbE media converter system to support data traffic over an 80,000 m transmission distance.
For a modern 10GbE media converter system, it is designed to support the fiber-optic based pluggable transceiver modules. The well-known fiber-optic based pluggable transceivers for 10GbE applications include the various types known as e.g. XENPAK, XPAK, X2, XFP and SFP+. With the help of these modules, multiple protocols, such as e.g. 10GBASE-SR/ -IR/ -ER/ -IRM can be supported by the same 10GbE media converter system, by exchanging the pluggable transceiver that is operated using the specific protocol specified by both the host system and its remote link partner.
Due to the similarity of mechanical construction, the same 10GbE media converter system designed for SFP+ pluggable transceiver module may also be used to support fiber-optic based and/or copper-cable based SFP pluggable transceiver modules that run formatted signals with lower data rate protocols, such as e.g. 1000Base-SX/ -IX/ -ZX specified by IEEE802.3z or 1000Base-T specified by IEEE802.3ab, respectively. For the 10GbE media converter system, the operating mode supporting SFP pluggable transceiver modules often refers to the so-called 1GbE bypass mode.
The 10GbE media converter is usually designed to have at least one channel including a par of ports, one port for connecting the CX4 copper cable to set up the link with the host system and the other one designed to support the fiber-optic based pluggable transceiver module to be connected to the remote link partner, respectively. By carefully selecting the pluggable transceiver modules and different types of the fibers, e.g. multimode fiber (MMF), or single mode fiber (SMF), a link distance from a few tens of meters up to 40000 meters can be achieved.
It is well-known practice to use a redundant system for the duplication of a critical link in a network such as the one described in FIG. 1 to ensure the network connectivity and reliability. In practice, the link protection is done by using at least two link lines, i.e. an active line, or working line, and a standby line, or a protecting line. If the link supported by the working line fails, the change of link status will normally be simultaneously notified by the redundant systems of both link partners at both ends of the link path, thus the redundant system of both link partners will simultaneously switch the data traffic onto the protecting line within typically a few tens of ms up to a few hundreds of ms. In such a way, network connectivity can be maintained and protected within the network configuration.
However, after introducing a media converter system in the link path of a network such as the one described in FIG. 2, the network connectivity may not be guaranteed anymore. This is because the media converter system creates an interconnecting node inside the link path, meaning that if a link failure occurs at one side of media converter system, such as e.g. at the fiber-optic link path side, the opposite link of media converter system, i.e. the side of copper link path, may still be set-up properly. Thus, the redundancy systems of both link partners will not be triggered to simultaneously switch the data traffic onto the protecting line, which will most likely lead to the complete loss of data traffic in the network. Thus, there are reasons to address the problem of network connectivity caused by the introduction of an interconnecting node.